Selection of Combined Continuous Lot-by-Lot Sampling Plans with Single Sampling Plan by Attributes as the Reference Plan

Sampling inspection is a product-control methodology and consists of procedures for making decisions on the disposition of lots of finished products based on the inspection of individual units in one or more random samples drawn from the lots or from the process. Lot-by-lot sampling by attributes and sampling plans for a continuous flow of products are the important classifications of inspection procedures. While lot-by-lot sampling is adopted when the inspection lots are formed from a production process, the concept of continuous sampling plans is used where the product flow is continuous and the formation of inspection lots is impractical or difficult. However, when the continuous production processes involve formation of lots, the concept of combined continuous lot-by-lot sampling plans, which incorporates the best features of the continuous and lot-by-lot inspection plans, can be considered as desirable for application. This paper studies the properties of such combined plans when a single sampling plan is used as a reference plan and presents a procedure for determining the parameters of the plan providing protection to the producer and the consumer.